MEPS 320:43-53 (2006)  -  doi:10.3354/meps320043

Trophic functioning with parasites: a new insight for ecosystem analysis

Jesús Ernesto Arias-González1,*, Serge Morand2

1Laboratorio de Ecología de Ecosistemas de Arrecifes Coralinos, Departamento de Recursos del Mar, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Mérida, Antigua Carretera a Progreso Km. 73 Cordemex, Mérida, Yucatán 97310, Mexico
2Centre de Biologie et de Gestion des Populations (CBGP-IRD), Campus International de Baillarguet, CS 30 016, 34988 Montferrier sur Lez Cédex, France

ABSTRACT: Several balance models of a coral reef ecosystem were created to determine if neglecting parasites significantly alters quantitative or qualitative ecosystem analysis. To better understand how these models react to the addition of parasites: (1) separate and joint analyses of parasitism in fish and benthos compartments were done, (2) it was assumed that parasites have predators or parasites, (3) the quantitative differences in parasites were evaluated and (4) microfauna were introduced into the models. From a quantitative view point the results were mixed; neglecting parasites seemed to cause small changes in conditions in some models. Qualitative differences were quite notable. Inclusion of parasites radically increased the number of pathways in the coral reef ecosystem model (from 362 to 7391), and increased mean trophic efficiency of the system (from 5.2 to 7.7%), resulting in a longer food chain (from V to VIII). Evaluation of quantitative differences in parasites showed that the models are very sensitive to parasite biomass, which varied from 0.60 to 0.06 g m–2. It is concluded that, even though introduction of parasites may not significantly change total flow of the modelled system, their omission may lead to high inaccuracy in web patterns (i.e. pathways) and trophic structure (i.e. trophic efficiency). Our results are similar to those from other studies of food webs and parasites that used different approaches.

KEY WORDS: Food webs · Parasites · ECOPATH with ECOSIM · Aquatic ecosystems · Coral reefs · Trophic efficiency · Ascendancy · Overheads

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